1. Field of the Invention
The present invention relates to a lens driving device suitably used for instance as a camera module of a mobile phone or so.
2. Description of the Related Art
In the lens driving device suitably used for instance as the camera module of the mobile phone or so, the device has been developed which carries out the blur correction by moving the blur correction movable part including a lens holder holding the lens in the perpendicular direction along the optical axis (for example refer to following patent document 1). In order to carry out the blur correction by moving the blur correction movable part in the perpendicular direction along the optical axis, a part of a first driving part having a first driving axis, and a part of a second driving part having a second driving axis are provided to a base part.
At the base part, an opening part is formed where at least part of the lens held by the lens holder is inserted. For the conventional devices, the opening part of the base part is formed in a circular shape to match with an outer shape of the lens. Also, in order to move the lens with respect the base part in the perpendicular direction against the optical axis, the inner diameter of the opening part is made larger than the outer diameter of the lens inserted to the opening part.
The size of the base part is preferably as small as possible in order to achieve a compact device. Therefore, if the inner diameter of the opening part which is formed at the base part is too large, the distance between the outer sides of the base part and the opening part is shortened, thereby the space to place the driving part on the base part will be lost. Thus, the inner diameter of the opening part is made to have minimum size necessary in accordance with the outer diameter of the lens.
Thus, it has been thought to design the inner diameter of the opening part of the base part so to secure the maximum moving amount along first driving axis direction of the lens, or to secure the maximum moving amount along the second driving axis direction of the lens. By designing as such, in case the lens moves only to the first driving axis direction or moves only to the second driving axis direction, there is no risk of lens colliding to the periphery of the opening part.
However, the lens does not necessarily move only along the first driving axis direction or only along the second driving axis direction, but for example, it also moves along the oblique direction positioned in middle of the first driving axis and the second driving axis. In the oblique direction, the lens moves along the moving vector corresponding to the sum of the moving vector along the first driving axis and the moving vector along the second driving axis.
Therefore, the moving amount of the lens in the oblique direction is longer by √2 times or so (about 1.44 times) at maximum compared to the moving amount along the first driving axis and the second driving axis; and in the worst case scenario, the lens might collide to the periphery of the opening part of the base part. When the lens collides against the periphery of the opening part of the base part, the lens might be damaged and also there may be a problem such as declined quality of blur correction or so due to the impact of the collision.
In order to avoid such problems, the opening part of the inner diameter which is unnecessarily larger compared to the diameter of the lens is formed at the base part. Therefore, it is difficult to make the size of the base part compact; hence as a result, it was unable to make the device compact.
[Patent document 1] JP Patent Application Laid Open No. 2011-65140